Thermal and fouling characteristics of cross-flowwet cooling towers undermixed weather conditions

Abstract: Cooling towers are widely used inmost industrial units to reject waste heat to the envi-ronment.Wet towers are usually designed to operate in hot and dry weather conditions, but wet cooling towers operating in Ahvaz climate suffer from mixed weather conditions that strongly affect the thermal performance of the towers. Operating inmixedweather conditions and fouling on fills are two major concerns for towers working in the direct reduction unit of Khuzestan Steel Company (KSC), Ahvaz. The first step is to model the thermal behaviour of the tower under the present operating conditions. Two mathematical models (the conventional Merkel model and the dimensionless Halasz model) are applied in this step and the results of the models for the outlet water temperature in nine various operating conditions are compared with experimental data. Prevailing fill characteristic curves for three cell halves of the tower are obtained using a numerical–experimental method. At the second step, the results of the chemical analysis of foul-ing material and circulating water are considered to obtain the main factor of scale forming in the tower. The tendency of water to scale forming is investigated using three conventional scaling criteria. The analysis of water and fouling material shows that both air and water have important fouling and scaling effects on fills. Finally, several approaches are proposed to reduce these dete-riorating effects of air and water. The effect of placing an impact separator in front of air louvers (to reduce suspended solids of the air) on the thermal performance of the tower is investigated